A significant population of all ages is confined to move in a wheelchair all or part of the time and these people face many challenges. While some of their problems are solved by the limited mobility afforded them through the wheelchair, other problems stem from the design of the chairs.
There are, at present, two major categories of wheelchairs: collapsible wheelchairs, which have fabric seats and backs and which can be collapsed sideways to make them easily transportable; and rigid wheelchairs which cannot be collapsed. The collapsible chairs are lightweight, relatively inexpensive, and transportable in the trunk or back seat of a car. Rigid frame wheelchairs, on the other hand, are relatively expensive and usually require a van or other specially prepared vehicle for transport.
For many patients it is desirable to have a chair which allows the position of the seat to be changed from the normal, level, position to one which is tilted back. Among other benefits this change in position changes the pressure distribution of the patient's body against the chair improving comfort. In the trade, this type of chair is known as a "tilt-in-space wheelchair". This feature is available only in wheelchairs having rigid frames. A patient is forced to choose between the lower cost and easy portability of a folding chair and the comfort, increased cost and inconvenience of a tilt-in-space wheelchair.
It is, therefore, an object of this invention to provide a tilt-in-space feature adaptable to a collapsible wheelchair. It is an object that the mechanism provided have sufficient lateral stiffness on each side of the wheelchair to obviate the need for cross bracing such as is found on rigid frame chairs.
Further, tilting a wheel chair could be accomplished by extending the length of the support means connecting the casters to the frame. This changes the angle which the caster assembly, particularly the vertical axis of rotation (ie. the swivel post) presents to the ground. However, the greater this angle varies from vertical, the poorer the performance of the caster. It is, therefore, an object of this invention to provide means of tilting a wheelchair without varying the vertical axis about which the caster assembly rotates.